Study On Structure Optimization Of New Partial Pressure Tool Under Low Injection Rate

Due to the heterogeneity of reservoir during oilfield development,most polymer solutions are injected into high permeability reservoirs,while the injection amount in low permeability reservoirs is less,which leads to poor oil displacement effect of polymer solutions in low permeability reservoirs and lower overall oil recovery.To solve this problem,on the premise of not changing the formation structure and polluting the formation,a partial pressure tool is proposed to control the injection amount of polymer solution in high permeability reservoirs,so that more polymer solution can be injected into low permeability reservoirs,thereby improving the overall oil recovery.However,due to the low permeability,thin reservoir thickness and small injection volume in the whole well,the original partial pressure tool can not control the injection volume of polymer solution in high permeability reservoirs under the condition of low injection volume,and the viscosity loss of polymer solution is large,which reduces the oil displacement effect.Therefore,a new partial pressure tool needs to be redesigned to meet the actual needs.In this paper,five new partial pressure tools are designed,and the parameter equations of pressure,velocity,viscosity and shear rate of polymer solution under the action of partial pressure tools with different structures are derived.At the same time,according to the concept of stability factor,the transition velocity equation of polymer solution in partial pressure tools is derived,which is used as the basis for selecting turbulence models.Then,the flow characteristics of polymer solution under the action of different partial pressure tools are studied by numerical simulation.The simulation results show that the pressure,velocity and viscosity of polymer solution change periodically under the action of partial pressure tools with different structures.When the cross-section of flow channel changes,the characteristic parameters change,and the degree of change is related to the structural characteristics of partial pressure tools.Then,an orthogonal test was carried out based on the results of numerical simulation,and the optimal structural parameters of a partial pressure tool with the largest pressure drop and the lowest viscosity loss rate of polymer solution were selected.The tool is an arc-shaped partial pressure tool with a distance of 0.5mm between the throttling groove and the outer cylinder,a convex circle radius of 1.5mm and a concave circle radius of0.5 mm.When the injection amount is 10m~3/d,it can produce a pressure drop of1.83MPa,and the viscosity loss of polymer solution is only 3.74%.Finally,a new arc-shaped partial pressure tool was designed and manufactured.The changes of pressure drop and viscosity loss rate of different injection amounts and different polymer solutions in the new partial pressure tool were studied through laboratory experiments,and compared with the numerical simulation results,and then compared with the original partial pressure tool to verify the effect of the new partial pressure tool.The research shows that,at low flow rate,the results of numerical simulation and laboratory experiments fit well,and the simulation results are more accurate.At the same time,the pressure drop of the original partial pressure is less than 1MPa and the viscosity loss rate is lower than 5%,while the new arc-shaped partial pressure fully meets the requirements.This study solves the problem that the original partial pressure tool can not produce higher pressure drop and lower viscosity loss rate under the condition of low injection rate,and also provides research ideas for solving the problem of low oil recovery in heterogeneous reservoirs.